In June, when UN security council approved a fourth round of trade restrictions, those who assented promised to impose focused sanctions this time: targeting Iran's powerful Revolutionary Guard and avoiding restrictions that are harmful to ordinary people. Two months later, the opposition is arguing that the effect has been precisely the opposite.

Some good moves have been made: in March, the US announced that even while sanctions remained in place, companies such as Google and Yahoo would be free to export web tools to Iran. But the beneficial effects of this have been overshadowed by the latest round of punitive measures.

Last week, Mir Hossein Mousavi and Karroubi co-authored a letter in which they tried to clarify the green movement's position on the new sanctions. They made it clear that they condemn the action, which, in their opinion, is disproportionately hitting the most vulnerable in the country.

They blamed President Mahmoud Ahmadinejad for mishandling the negotiations over Iran's nuclear activities but emphasised that sanctions imposed internationally are adversely affecting the farmers, workers and poor people of Iran.

Karroubi is also right when he says that a North Korean or Cuban model, according to which Iran is isolated from the global community, will give the regime freer rein to continue its repression of people without bothering about the consequences internationally.

We can see this in the regime's indifference to the international outcry over the stoning sentence imposed on Sakineh Mohammadi Ashtiani, a 43-year-old mother of two.

A year ago, Iran released an Iranian-Canadian journalist, who was imprisoned in the aftermath of Iran's disputed election in June 2009, under pressure from the international community, including an appeal issued by the US secretary of state, Hillary Clinton.

This week, Clinton joined international condemnations of both Ashtiani's sentence and the authorities' imminent execution of an 18-year-old boy on charges of sodomy. This time, however, just a day after Clinton's remarks, Ashtiani was made to go on TV where she confessed she was accomplice in murdering her husband.

Add to that the plane crashes in which scores of innocent people have been killed and hundreds injured due to a lack of spare parts, and you have a picture of sanctions increasing the misery of the people, not its government.

Karroubi is right: sanctions have just crippled ordinary Iranians, trapped not only by their own government, but by action taken in the name of the international community.